1. Field of the Invention
This invention relates to a recording head comprising pressure chambers in communication with nozzle openings, and thin piezo-electric vibrating plates bonded to parts of the pressure chambers, wherein the pressure chambers are compressed by the piezo-electric vibrating plates to form ink droplets, and more particularly to an ink jet recording head in which a piezo-electric board, pressure chamber forming members, and an elastic board are provided in the form of multi-layers.
2. Related Art
A conventional ink jet recording head includes piezo-electric vibrating plates bonded to portions of an elastic board where pressure generating chambers are formed, wherein the piezo-electric vibrating plates are bent to change the volumes of the pressure generating chambers to form ink droplets. This ink jet recording head is advantageous in that the ink droplets are formed stably because the pressure generating chambers are widely changed in volume.
A conventional ink jet recording head of this type has been disclosed by Japanese Patent Application (OPI) No. 40030/1994 (the term "OPI" as used herein means an "unexamined publication application"). This type of recording head is formed by sintering green sheets. More specifically, an elastic board of ceramic which is formed into a vibrating member, a pressure-generating-chamber forming member which forms pressure generating chambers, and a lid member of ceramic which seals a surface of the pressure-generating-chamber forming member and which has communicating holes through which the pressure generating chambers are in communication with an ink supplying hole and communicating holes through which the pressure generating chambers are in communication with nozzle holes are joined together. Electrodes are formed on the elastic board, and in addition piezo-electric vibrating plates are formed on the elastic board by sintering piezo-electric material, to form an ink pump member.
The ink pump member thus formed is adhesively bonded onto the laminate which is made up of: an ink-chamber forming board of metal which has a common ink chamber; and a nozzle member which has nozzle openings.
In the case where the piezo-electric vibrating plates are employed as actuators for expanding and contracting the pressure generating chambers, in order to simplify the adhesion work or to improve the reliability of the adhesion, a method is employed in which a green sheet of piezo-electric material is applied to the vibrating plates, and sintered.
However, the above-described method of forming a conventional ink jet recording head suffers from the following difficulties The piezo-electric material contracts during sintering, so that the ink pump member bends or swells. Hence, especially in the manufacture of a high-resolution recording head in which, for instance, ninety (90) nozzle openings are arranged in one line per 2.54 mm, it is rather difficult to join the ink pump member to the laminate of the common ink chamber forming board and the nozzle plate. Even if the ink pump member is joined to the laminate, the nozzle openings are adversely affected in their orientation, so that the resultant print is low in quality.
On the other hand, the ceramic material contracts when sintered. Therefore, even if it is sintered with its rate of contraction taken into account so that it is positioned accurately with respect to the common-ink-chamber forming board and the nozzle plate which are not contracted, errors occur depending on the sintering conditions and the delicate variation in composition of the ceramic material. As a result, in the manufacture of the above-described high-resolution recording head, the yield is low.